Due to the rising cost of liquid fuel (e.g. diesel fuel) and ever increasing restrictions on exhaust emissions, engine manufacturers have developed dual-fuel engines. An exemplary dual-fuel engine provides injections of a low-cost gaseous fuel (e.g. natural gas) through air intake ports of the engine's cylinders. The gaseous fuel is introduced with clean air that enters through the intake ports and is ignited by liquid fuel that is injected during each combustion cycle. Because a lower-cost fuel is used together with liquid fuel, cost efficiency may be improved. In addition, the combustion of the gaseous and liquid fuel mixture may result in a reduction of harmful emissions.
Engine parts near the cylinders may be exposed to high temperatures associated with fuel combustion. For example, in a dual-fuel engine utilizing gaseous fuel injectors at each cylinder's air intake ports, the efficiency and integrity of the injectors may be materially affected by the extreme temperatures. Various cooling systems have been developed to cool injectors to workable temperatures and to achieve desirable efficiency and part lifetime.
An exemplary arrangement for cooling a liquid injector is disclosed in U.S. Pat. No. 7,021,558 that issued to Chenanda et al. on Apr. 4, 2006. In particular, the '558 patent discloses a liquid fuel injector having a cooled lower nozzle body. The liquid fuel injector includes an additional fuel passage in the lower nozzle body that receives a metered amount of fuel. This additional passage provides greater surface area over which fuel can flow. The additional surface area improves cooling of the liquid fuel injector by exposing more of the lower nozzle body to the relatively low-temperature fuel.
Although the design in the '558 patent may improve cooling of a liquid fuel injector, its applicability may be limited. For instance, the use of a single cooling passage may limit the cooling effect. In addition, other parts of the injector, such as electrical components, may not be sufficiently cooled by the additional passage inside the lower nozzle body. Further, the additional passage may not be practical for gaseous fuel injectors that typically require larger nozzles with fewer restrictions.
The disclosed fuel system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.